Dr. Mitchell L. Gaynor, a Manhattan oncologist and popular author who taught cancer patients to supplement conventional medicine with soothing music, diet and meditation — and practiced what he prescribed — was found dead on Tuesday at his country home in Hillsdale, N.Y. He was 59.

The cause was suicide, said Kevin Skype, senior investigator for the Columbia County sheriff. Further details were not available.

Dr. Gaynor, the son of a West Texas dentist, built both a distinguished medical career and a public following. The founder and president of Gaynor Integrative Oncology in Manhattan, he had been a clinical assistant professor at Weill Cornell Medical College, also in Manhattan, and director of medical oncology at the school’s Center for Integrative Medicine.

He was also the author of six books, many of them focused on the environment’s effect on an individual’s health and geared for a general readership. They include “The Healing Power of Sound” (1999), “Dr. Gaynor’s Cancer Prevention Program” (1999) and “Nurture Nature, Nurture Health” (2005).

In 2013, Jon Regen, a jazz and pop pianist and son of a patient of Dr. Gaynor’s, joined with him to produce a record titled “Change Your Mind.” After it was featured on “The Dr. Oz Show,” the record topped Billboard magazine’s New Age charts. They recorded two other albums, “Uplift” and “Peaceful Sleep.”

Dr. Gaynor, who received a traditional medical education and continued to recommend traditional cancer treatments, was a postdoctoral fellow at Rockefeller University in Manhattan in 1987 when he became fascinated by integrative oncology, which encompasses both conventional and alternative treatments — a hybrid that its detractors call pseudoscience. At the time, research was being conducted at the university into nutrient-gene interactions and the immune system.

“I was amazed at the fact that we really ‘are what we eat,’ and that with the best medical training in the world, nobody had ever taught me this,” he said in a 2013 interview.

In 1991, Dr. Gaynor was at New York Hospital treating a refugee Tibetan monk named Odsal who was found to have a rare cardiac condition. He concluded that the monk, dislocated from his homeland, “was literally suffering from a broken heart.”

Dr. Gaynor tutored Odsal in his own style of meditation. The monk reciprocated by bringing a traditional Tibetan metal singing bowl to the doctor’s Manhattan apartment.

“We removed our shoes and settled ourselves cross-legged on the living room floor,” Dr. Gaynor wrote in “The Healing Power of Sound.” “Odsal took out a small wooden baton and moved it lightly around the rim of the bowl, in much the same way you might trace the lip of a wineglass with your finger.”

“The sound — a rich, deep note with a strong vibrato that resembled nothing I had ever heard before — was so exhilarating that tears of joy sprang to my eyes,” he continued. “I could feel the vibration physically resonating through my body, touching my core in such a way that I felt in harmony with the universe.”

“I immediately intuited that playing the bowls would change my life,” he wrote, “and the lives of many of my patients.”

Most of the nutritional supplements and alternative treatments he recommended were aimed at fortifying a patient’s immune system and targeted what he determined were the root causes of disease.

When people are relaxed as a result of meditation, chanting, listening to music, breathing exercises or other behavioral therapy, Dr. Gaynor said, their heart rates are steady, their breathing is deep and slow and their stress hormones decrease, allowing the immune system to function more efficiently, lowering blood pressure and releasing natural opiates.

Dr. Gaynor distinguished between curing a patient — fixing a physical symptom — and healing, which he described as a complementary union of mind, body and spirit.

“If somebody had told me when I was a medical student in Dallas, Texas, that one day I would be teaching my patients to use singing bowls to heal themselves, I would have thought he or she was crazy,” Dr. Gaynor wrote.

Mitchell Lee Gaynor was born in rural Hale Center, Tex., on June 5, 1956, the son of Dr. J. Irvin Gaynor and the former Elaine Shure.

His father “wouldn’t charge the patients who couldn’t pay, and they would come by the house to bring corn, vegetables, whatever they had,” Dr. Gaynor told Alternative Medicine magazine in 2003.

His mother died of breast cancer when he was 9. “I saw from my mother how people could have equanimity and inner peace in the presence of significant physical suffering and illness,” he said.

Dr. Gaynor graduated from the University of Texas in 1978 and from its Southwestern Medical School four years later before becoming chief medical resident at what is now NewYork-Presbyterian Hospital/ Weill Cornell Medical Center.